Based on my experience, the acumulator failing symptom is rapid cycling of the PM as the unit tries to rebuild pressure.
Too much of this and the motor/pressure switch will fail, causing high pedal effort and inability to stop.
Options:
1) Order a reman Powermaster and replace
2) Covert to Vacuum using parts from another G-body + change the billet vacuum block
3) Convert to Hydroboost
OF these 3 choices, IMHO the conversion to vacuum is the least expensive, but you will need the pedal assembly from the donor car (or at least the pedal and all the little pieces)
Hydroboost systems can be pieced together by using OE parts from diesel powered G-bodies and splicing in the low pressure side. Discussions here will give you part numbers that you will need... and you can utilize the existing pedal.
Replacing the PM is the straightforward method... but pricey.